Helical pile installation is increasingly common in the railway industry due to the speed and safety with which they can be installed. In Derby, we assisted with the installation of a 7M rail signal for Network Rail using our patented ScrewFast helical piles.
Helical Pile Specifications
There were 8 Screwfast helical piles and each was two metres in length. In this instance the piles were two metres long because we needed to keep below the overhead wires utilised by Network Rail. The overhead wires were also switched off during installation, for safety purposes. The length also keeps the piles at a manageable lifting weight while enabling the installers to easily reach up and screw in the bolts.
The tube thickness (the thickness of the walls of the pile) enables the piles to take compression or tension as needed, depending on a variety of factors. The top piece is galvanised; this is additional protection in the aerobic zone where corrosion takes place.
Torque Motor Dial Readings: The Importance of Precision
On the side of the green torque motor you’ll see a dial- that dial is calibrated in kilonewton metres (kN·m). The reading on that dial is vital as it confirms that the pile has been installed into competent soil, to the required torque.
The dial increases as each pile is installed and it’s important to average the torque over the last metre. The last pile was installed. Previous piles had averaged 12-16 kN·m, which is a good range.
The final level reading was taken using a laser level, which is often our measurement tool of choice. The installation motor rate (the torque rate) is slowed down to give a correct reading on the dial. If you were to try to rush the pile in at high speed you would get a false reading. This is why the machine is always slowed down during the final installation push.
In 3 hours, eight piles were successfully installed. The total installation took just over 3 ½ hours to complete. The signal was 7m high and had a 5m cantilever with a 363kN·m overturning moment. As mentioned, it was supported on 8 ScrewFast piles, each of which are 2M long.
For more information about this project, or any of our helical and screw piling services, contact ScrewFast today.
Categorised in: helical piles